Mechanism of hopping magnetoresistance in antiferromagnetic dielectrics - Application to La2CuO4
Abstract
A model of a spin mechanism of hopping magnetoresistance in dielectrics with a complex magnetic structure is outlined. The concept is based on the splitting of impurity states with respect to spin in a molecular field and on the difference of hopping probability with and without spin flip. As a consequence, the resistance depends on the magnitude and mutual orientation of the molecular fields acting on the impurity spins. A theory for La2CuO4 is detailed and the magnetic phase diagram is plotted. An interpretation of experimental results indicates that the symmetry of the impurity state allows only a molecular field that is connected with the asymmetric part of the exchange and that local enhancement of the orthorhombicity arises near a localized hole. It is proposed that this may offer a confirmation of the polaron effect in La2CuO4 which is important for an understanding of the nature of the current carriers and of superconductivity.
- Publication:
-
Zhurnal Eksperimentalnoi i Teoreticheskoi Fiziki
- Pub Date:
- August 1990
- Bibcode:
- 1990ZhETF..98..681G
- Keywords:
-
- Antiferromagnetism;
- Copper Oxides;
- Dielectrics;
- High Temperature Superconductors;
- Lanthanum Oxides;
- Magnetic Properties;
- Crystal Lattices;
- Magnetic Fields;
- Mixed Oxides;
- Spin;
- Superconductivity;
- Solid-State Physics